1. Field of the Invention:
The present invention relates to a toilet bowl flushing device for supplying flushing water to a toilet bowl to wash out the same.
2. Description of the Relevant Art:
There are well known toilet bowl flushing devices having a flush valve or a solenoid-operated valve for supplying a rush of flushing water to the toilet bowl to cleanse the same after it has been used by a user.
One solenoid-operated valve assembly for use in such a toilet bowl flushing device is disclosed in Japanese Laid-Open Patent Publication No. 60-136684, for example.
The disclosed solenoid-operated valve assembly is schematically shown in FIG. 41 of the accompanying drawings. The solenoid-operated valve assembly has a body 341 defining therein a flow passage 344 having an inlet 342. The body 341 houses a shutoff cock 345, a filter 346, and a solenoid-operated valve 347 which are arranged successively down-stream from the inlet 342 with respect to the direction in which water flows through the flow passage 344. A tubular body 354 is installed on the body 341 in communication with the flow passage 344 and has an outlet 343.
The shutoff cock 345 comprises a valve member 348 and a valve holder rod 349. Normally, the valve holder rod 349 is in an upper position, as illustrated, and the valve member 348 is lifted under water pressure to open an opening 350, thus allowing flushing water to flow through the flow passage 344. For stopping the supply of flushing water, the threaded portion of the valve holder rod 349 is turned to lower the valve holder rod 349 to press the valve member 348 against its valve seat, thereby closing the opening 350.
The solenoid-operated valve 347 comprises two axially juxtaposed cylindrical electromagnetic coils 351, 352, a plunger 353 inserted centrally in the coils 351, 352 and axially movable when the coils 351, 352 are energized, and a valve member 356 engaging the lower end of the plunger 353 for selectively opening and closing an opening 355a defined in a valve seat 355.
When the coils 351, 352 remain de-energized, the plunger 353 is pressed downwardly under the bias of a spring 357 to cause the valve member 356 to close the opening 355a. When only the coil 351 is energized, the plunger 353 is elevated a predetermined distance, and the valve member 356 is displaced upwardly under water pressure to allow a smaller amount of flushing water to be discharged from the solenoid-operated valve 347. When both the coils 351, 352 are energized, the plunger 353 is lifted a larger distance to allow a larger amount of flushing water to be discharged.
Where the solenoid-operated valve assembly of this type is incorporated in a toilet bowl flushing device, therefore, different amounts of flushing water for respective defecation and urination use can selectively be discharged to flush the toilet bowl under the control of electric signals.
The toilet bowl flushing device can however select only one of two modes at a time, i.e., a mode in which a smaller amount of flushing water for urination use is supplied to the toilet bowl and a mode in which a larger amount of flushing water for defecation use is supplied to the toilet bowl. In each of these modes, the flushing water can only flow of its own accord in a fixed flow rate pattern that is determined by the water pressure, the diameter of the pipe used, and other parameters. It is not possible to control the flow rate of supplied flushing water in one flushing cycle such that the flow rate of flushing water will vary with time.
The toilet bowl flushing capability is largely governed by the configuration of the toilet bowl, the pipe arrangement, the flow rate of flushing water, the water pressure, and other factors. The fixed flow rate pattern in which flushing water flows of its own accord cannot give the maximum bowl flushing ability to individual toilet bowls, and may supply different toilet bowls with an unduly large or small amount of flushing water.
Japanese Laid-Open Patent Publication No. 61-109832, for example, discloses a toilet bowl flushing device which has a preliminary flushing mode for discharging a smaller amount of flushing water before the toilet is used to provide an increased flushing ability, in addition to a main flushing mode for discharging a larger amount of flushing water to wash out the bowl after it has been used. The disclosed toilet bowl flushing device includes a seating sensor for detecting when the user is seated on the bowl. In response to a signal from the seating sensor, a solenoid-operated valve disposed in a water supply piping system coupled to the toilet bowl is operated to discharge a smaller amount of flushing water into the toilet bowl before the toilet is used by the user.
In the above toilet bowl flushing device, however, since the flow rate of flushing water is controlled by the solenoid-operated valve of the general design, the flow rate of flushing water cannot precisely be regulated. While only a very small amount of flushing water is required in the preliminary flushing mode, a greater amount of flushing water than necessary may be discharged by the flushing device in the preliminary flushing mode, which is wasteful of flushing water. Furthermore, a trap tube connected to the toilet bowl may run short of sealed water, or a water hammer may occur in the piping system.
Generally, the water discharge piping system extending from the toilet bowl has a trap tube integrally coupled to the toilet bowl for siphoning water from the bowl to wash out the bowl effectively. In order for the trap tube to siphon water from the bowl, at least the trap tube must be filled with water. With the conventional arrangement, since flushing water is discharged even until the trap tube is filled with water, a far more amount of flushing water has to be supplied than the amount of flushing water discharged, and hence the amount of flushing water used is increased.